電感是開關電源中常用(yong)的(de)元(yuan)件(jian)由(you)于電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)壓(ya)相位不同，理論上(shang)沒(mei)有(you)損耗。電(dian)(dian)(dian)感為(wei)儲能元(yuan)件(jian)，與電(dian)(dian)(dian)容一起用(yong)在輸入濾波(bo)和輸出濾波(bo)電(dian)(dian)(dian)路上(shang)用(yong)來(lai)平滑電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)。電(dian)(dian)(dian)感也被(bei)稱為(wei)扼流(liu)(liu)(liu)(liu)圈特點是流(liu)(liu)(liu)(liu)過其上(shang)的(de)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)有(you)“很(hen)(hen)大(da)的(de)慣性(xing)”。換句話說由(you)于磁通連續(xu)特性(xing)，電(dian)(dian)(dian)感上(shang)的(de)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)必須連續(xu)否(fou)則會產生(sheng)很(hen)(hen)大(da)的(de)電(dian)(dian)(dian)壓(ya)尖峰(feng)（感性(xing)元(yuan)件(jian)，如果(guo)突然斷電(dian)(dian)(dian)（電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)回路被(bei)切(qie)斷），會產生(sheng)很(hen)(hen)大(da)的(de)電(dian)(dian)(dian)壓(ya)尖峰(feng)脈沖損壞與之(zhi)串聯的(de)器件(jian)，此時必須加續(xu)流(liu)(liu)(liu)(liu)二極管續(xu)流(liu)(liu)(liu)(liu)！！！）。

　　電感常被理解為開關電源輸出端中的LC濾波電路中的L（C是其中的輸出電容）。雖這樣理解是正確的，為了理解電感的設計必須深入的了解電感的行為。在降壓轉換中，電感的一端連接到DC輸出電壓另一端通過開關頻率切換連接到輸入電壓或GND。
　　Buck/Boost型開關電源隨開關管的開關，儲能電感的電流波形等價于直流IDC上加一個I(P-P)值為ΔI的交流。因而IDC成為輸出電流IO主要消耗在負載上；交流ΔI消耗在負載電容的ESR（EquationSerial Resistance）上成為輸出紋波Vripple。
　　所以紋波電(dian)(dian)(dian)流(liu)(liu)(liu)的大(da)小同樣會影響電(dian)(dian)(dian)感器和輸(shu)(shu)出電(dian)(dian)(dian)容(rong)的尺寸紋波電(dian)(dian)(dian)流(liu)(liu)(liu)一般設(she)定為最大(da)輸(shu)(shu)出電(dian)(dian)(dian)流(liu)(liu)(liu)10%～30，因(yin)此(ci)對于(yu)降壓型(xing)電(dian)(dian)(dian)源(yuan)來說流(liu)(liu)(liu)過電(dian)(dian)(dian)感的電(dian)(dian)(dian)流(liu)(liu)(liu)峰值比電(dian)(dian)(dian)源(yuan)輸(shu)(shu)出電(dian)(dian)(dian)流(liu)(liu)(liu)大(da)5%～15%之間(jian)。